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Re: Some questions about the Shark driver

ok so i just finished a 3 day build using the shark a 12V SLA and 5 XR-E's in series.
I AA'd the shark ( back side ) to a piece of aluminium 10cm long x 3cm wide x 3mm thick which was in turn aa'd to a piece of aluminium hollow section 10cm x 10cm x 20cm long with 3mm thick walls so i guess it has ample heatsinking.
i connected the external pot and wiring as instructed and filpped the switch.
it worked wonderfully and hardly got warm.
so with it turned on i started marking the pot with incremental 100mA positions, when i got to 800mA it went very dim and no matter how many times i turn the pot to and fro it stays very dim. i checked the wiring again and everything was ok. i measured the Vin at the led string and it is reading 12.5V i.e. same as battery.
Therefore the shark is no longer boosting but it is still getting warm, What happened ?
How do i fix it ?

Re: Some questions about the Shark driver

I only guessed as if it's pressed down it may be isolated but once it heats up it presses into the board from expansion, but yeah you put a ton of AA on there. I dont know what else I'd check other than make sure your POT is still working and connections?

Re: Some questions about the Shark driver

First, make sure it's a problem with the shark. See if the LED's work fine and make sure the battery pack is good. Make sure none of the bare sections of the wires are touching anything, make sure all the traces are intact, make sure all the solder is where it's supposed to be.

Got busted lights? Send me a PM and depending on the situation, I'll take 'em off your hands. I always like a good modding challenge.

Re: Some questions about the Shark driver

it's not a battery pack, it's an SLA which i just bought and seems to be working properly. i removed all wires and re soldered them making sure nothing is touching. i did not touch the traces nor the soldering, except for removing the pot and it's still not boosting. When turned on it does go bright for a split second but immidiatly goes very very dim after that ( dd from battery )

i also removed the j1 jumper, connected it to a 3.6V batt and checked the Vf where the led is supposed to be and it was still 3.6V where as it should be 11V if im not mistaken.

Re: Some questions about the Shark driver

So if I use an external pot, is it better to AA it down to backside or the front side? I read somewhere that AAing the front side with all the components would be better for thermal managment. Is the AA epoxy conductive enough to short anything?

Re: Some questions about the Shark driver

One more question for the shark board, I want to drive a single Seul in a 3d M@g using standard alk's or ni-mh cells.

1. Is the shark appropriate for this role?
2. Now the the minumum input is stated as around 2.7v. Does this mean under this Vin the converter will not fire up?
3. will the converter continue to operate as the cell voltage drops.

Re: Some questions about the Shark driver

Originally Posted by Amonra

it's not a battery pack, it's an SLA which i just bought and seems to be working properly. i removed all wires and re soldered them making sure nothing is touching. i did not touch the traces nor the soldering, except for removing the pot and it's still not boosting. When turned on it does go bright for a split second but immidiatly goes very very dim after that ( dd from battery )

i also removed the j1 jumper, connected it to a 3.6V batt and checked the Vf where the led is supposed to be and it was still 3.6V where as it should be 11V if im not mistaken.

I'm not sure what happened. Under normal conditions it's pretty robust. Turning the trim pot on the board all the way around shouldn't kill the converter board. Even when the wiper is not connected it should run max current (1A).

Floating the wiper contact will either float high and give you 1A output or float low and give you ~10% of full output.

As for more Sharks we are running another batch as we speak. They should be available in a week or so.

Re: Some questions about the Shark driver

Pls feel free to jump in if you think I'm wrong....

I've got some experience with electronics. I would say you have to heatsink from the component side, not the pcb side. It's the components that will get hot. Some heat will get through to the non-component side via the lead solder and I see this is a two sided pcb but fiberglass board makes a poor heat conductor. You may fry the components before the heat can be pulled away.

I have a SHARK in front of me now, and I can see what looks like an external zenner diode (which eats into the efficiency - so it will get hot).

I don't see any external switch (fet) so it must be internal to the controller ic.

All the components are different heights, so heatsinking them will be difficult unless you just throw a load off Thermal Epoxy all over (electrically non-conductive).

Only problem with this is that you then loose the ability to move the current potentiometer. Just make sure you set the current before you epoxy it to the heatsink.

Re: Some questions about the Shark driver

Take a good look at the bottom of the shark board. There is a patch of what looks like tiny metal holes under where the IC is mounted. This metal square goes THROUGH the PCB to make thermal contact with the IC. It is a thermal via. When you pot the board in Arctic Alumina from the bottom, some of the AA will migrate into the little holes, and provides a thermal pathway to the sink. I suspect that the IC itself is mounted with thermal compound to the top of this thermal via. It will be the shortest pathway thermally because the IC will get the hottest on the bottom. This is because the actual components inside the IC are very close to the bottom of the DIP package. Heat sinking on the component side of the board will not be nearly as efficient.

Re: Some questions about the Shark driver

just a question: while removing the preset pot connected to the shark to add an external pot i accedentally ripped the track which is on the left hand side under the preset pot. whilst trying to fix my f@#k up i accidentally continued to rip the track (very narrow and delicate) which leads to a very small surface mount resistor which then splits into two legs of the IC. i accedentally also ripped this very small resistor whilst trying to fix it. i then conected the pot to the bridge where the two legs of the IC are connected as there was more of a surface area to solder. and it seems that the shark works correctly.
So my question is how important is that very small resistor ?
can i do without it ?
is there a way by which i can fix my F#$K up ? ( maybe i can add an external resistor ? )

Re: Some questions about the Shark driver

Originally Posted by CodeOfLight

Take a good look at the bottom of the shark board. There is a patch of what looks like tiny metal holes under where the IC is mounted. This metal square goes THROUGH the PCB to make thermal contact with the IC. It is a thermal via. When you pot the board in Arctic Alumina from the bottom, some of the AA will migrate into the little holes, and provides a thermal pathway to the sink.

Most of the via holes on my board are full of solder. And there are no vias beneath the zenner diode which will dissipate the most heat.

Originally Posted by CodeOfLight

I suspect that the IC itself is mounted with thermal compound to the top of this thermal via. It will be the shortest pathway thermally because the IC will get the hottest on the bottom. This is because the actual components inside the IC are very close to the bottom of the DIP package. Heat sinking on the component side of the board will not be nearly as efficient.

when I hold the board up to a light, I can see beneath the diode, it is therefore not heatsinked to the pcb.

I've run 14W through this board (12W to leds, 1.6A input current, leaving 2W dissipated by the converter) while holding my fingers on the diode and linear converter IC. After a few minutes, the components got quite hot. The under side of the pcb was quite cool in comparison. This could have been because I was not using aae in the vias though. I doubt adding aae to the underside would have helped much if most of the holes were filled with solder to begin with. As I've also said, the diode has no vias beneath it at all.

I've heatsinked mine from the component side and it seems to be working fine. I'll do some extended run time tests ans let you know what I find. I've asked for clarification on this from Wayne, but I think he's busy at the moment.

I'm not saying you're wrong CodeOfLight about vias on pcb's. I just wonder how effective they will be on this board given their placement and manufacturing execution.

Re: Some questions about the Shark driver

The IC has a hidden pad under the IC which you can not see. That pad is soldered to the holes under the IC. This is the optimum thermal path for the IC and I would recommend filling the holes with more solder. This makes a solid core between the bottom pad of the IC to the bottom of the board.

From there it there are many solutions to connect the bottom to a heat sink. Thermal epoxy has worked fine for all my mods. But, I don't push the Shark that hard so that's not necessarily saying anything.

Some suggestions:

1) Cut a 0.030 copper disc into two and solder each half onto the two areas that have the vias on the bottom side of the board. This will give you a 0.030" standoff of copper. Using Teflon 250V 26AWG stranded wire it's diameter is approximately 0.030" and the LED wires can be soldered on the backside and then bent 90 degrees to hug the bottom of the board. This should allow you to sill press the PCB so that the copper disc make mechanical contact to the heatsink and with thermal epoxy provide a good thermal bond between the board and the heat sink.

2) Build up solder in place of the copper discs where the vias are and use them for standoffs.

Both the IC and the schottky diode need good thermal heatsinking. These are the two primary heat generators and both the IC and diode have vias near them allowing backside heat sinking.

Re: Some questions about the Shark driver

I got my shark today and am amazed at how small it acually is. A little too small. I'm just wondering how you solder on a board this small. I want to put an external pot on it and replace the .10 ohm resistor with two .15 ohm resistors to set the current limit at 1,500 ma. How do you solder on such tiny components? Does just a soldering iron and a steady hand do the trick, or is there something else that is very helpfull in doing this?

Re: Some questions about the Shark driver

Originally Posted by EatSleepRunBike

I got my shark today and am amazed at how small it acually is. A little too small. I'm just wondering how you solder on a board this small. I want to put an external pot on it and replace the .10 ohm resistor with two .15 ohm resistors to set the current limit at 1,500 ma. How do you solder on such tiny components? Does just a soldering iron and a steady hand do the trick, or is there something else that is very helpfull in doing this?

Howdy Eatsleeprunbike,

You should go back and read post #9 of dat2zip`s. I really don`t know anything about this stuff but I am trying to learn. I believe changing from .10 ohm resistor to .15 ohm will lower the current instead of raising it. Does .075 ohm resistor sound right for 1,500ma?

Re: Some questions about the Shark driver

Originally Posted by kenster

Howdy Eatsleeprunbike,

You should go back and read post #9 of dat2zip`s. I really don`t know anything about this stuff but I am trying to learn. I believe changing from .10 ohm resistor to .15 ohm will lower the current instead of raising it. Does .075 ohm resistor sound right for 1,500ma?

Ken

He is going to use two two 0,15 ohm resistors in parallel, I guess. Together they act as if they were one 0,075 ohm resistor.

-N

My mods. Please post questions about my mods to the corresponding thread: like that all CPFers can get the info - thanks!